The distinctive feature of this astatic magnetometer is that this is set on a 4 square meter sheet of galvanized iron and has no damper, as shown in Figs. 1 and 2.
Through several years of experiment, the writer discovered that this magnetometer can record short period change of magnetic field.
The period is 1/10-2 second.
The writer proved that the induced magnetic field in the galvanized iron sheet can oscillate this magnetic needle, because of the difference of vertical distance of two magnetic needles, as shown in Fig. 2.
Figs. 7 and 8 show the relation between the oscillation of magnetic needle and earthqakes.
Through the writer's records, it is proved that change of temperature, magnetic storm and daily change of magnetic field and thunder can not be recorded by this magnetometer and that the reason is that they have not 1/10-1 second change of magnetic field.

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Observation of microseisms is being performed by the tripartite network, ΔPQS, which is established in the compound of Tokyo Gakugei University in Koganei-shi, Tokyo. This report deals, in the first place, with the graphical method to obtain the direction from which microseisms came, then it discusses the relationship between the propagating direction of microseisms and period and the meteorological and oceanographical conditiions, on the basis of the microseismograms recorded during the period of July to November, 1962, as tabulated in Table 1.
In each of Figs. 6 to 10, the upper figure shows the directions from which the microseisms arrived. The direction is divided into sections of 45° each, and the number of microseismic waves that reached the respective sections is represented by percentage. The middle figure shows the frequency distribution of period. The lower figure is the weather map of the day of observation.
The above results are summerized in the following.
1. Microseisms observed in Tokyo were closely related to the oceanographical and meteorological conditions of the Pacific coast and its offing, north of the Boso Peninsula. When a typhoon, or a cyclone or a cold front, occurred over the sea north of the Boso Peninsula and the sea was more or less rough, the microseisms reaching Tokyo were predominantly from E or NE. In case the typhoon, or cyclone or front, was located near the coast, the period of the arriving microseisms was mostly 4 to 5 seconds, but if the typhoon existed in the distant offing (near or on the outer side of the Japan Trench), the period and the amplitude of the microseisms were apt to become remarkably large.
2. In case a typhoon occurred over the southeastern ocean and a front in the northeastern offing, microseisms coming from SE were observed along with those predominantly from E or NE.
3. When a typhoon occurred in the southwestern or western offing, with a cyclone or a front in the northeastern offing, and the sea along the Pacific coast of Japan was rough, the microseisms arriving at Tokyo were fairly distinctly classified into two directions, SW and NE or E.
4. From the 16th to 17th of November, 1962, the sea north of the Boso Peninsula was comparatively calm, and Typhoon No. 28 at about 800km southwest of the mainland of Japan was moving eastward at a considerable speed. The microseisms then observed in Tokyo were predominantly from the direction in which the typhoon's center was located at the time of 19 to 20 hours earlier than the observation time, and the direction changed with the typhoon's movement. The occurence of these microseisms may be explained as follows: The swells, having the period averaging about 14 seconds, were caused by the wind of the velocity about 25m/sec in the storm zone (within the 150km radius); these swells, traveling at the velocity about 15m/sec, approached the mainland, and there they gave to the microseisms due to the Longuet-Higgins mechanism.
The writer intends to accumulate more data in order to confirm the abovementioned results.

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In order to clarify the physical properties of Rayleigh type dispersive waves (M waves), we investigated, using machine methods of computation, dispersion curves and vertical distribution of amplitudes for the medium composed of elastic stratum over an infinitely rigid solid.
We treated for the first three modes (M₁₁, M₂₁, M₁₂, M₂₂, M₁₃, M₂₃) under several condition of Poisson's ratio, and found out that both dispersion curves and amplitude distributions exchange their properties each other between M₁ type waves and M₂ type waves only when the Poisson's condition is satisfied in the superficial layer. Furthermore, the higher the modes or the nearer the Poisson's ratio approches 0.25, the more complicated become the changes of rotational direction of particle motion at the surface. And it seems worth while to state that, above certain values of L/H (L: wave length, H: thickness of the superficial layer), the particle motion for the M₁ type waves is of a progressive rotation and for the M₂ type waves of a retrograde rotation, regardles of elastic parameters.
Finally, some considerations on the classification of the M waves are added to.

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The theoretical studies on the P and S waves radiation from a spherical cavity on which the stress τ_z=(Fy/a)exp(ipt) acts was investigated by J. G. J. Scholte and A. R. Ritsema (1962), where y and z are rectangular coodinates and F is an arbitary constant. The stress is similar to the force system of a single couple with moment in the theory of focal mechanism. In their paper, only periodic solution was discussed, and the radiation pattern of S waves depends on the value of the ratio of its wavelength to the radius of the cavity (a).
In this paper, the time variation of the stress is considered as a step function, and main results obtained are as follows.
1. The wave form of S waves depends on θ in spherical coordinates (r, θ, φ).
2. Generally speaking, the orbit of a particle motion of S waves is not linear.
3. If it is assumed that the displacement direction of S waves at maximum amplitude represents its motion direction, its radiation pattern is intermediated between that for a single and a double couple point source, and is similar to the radiation pattern, obtained by Scholte et al., in the case when the wavelength is very large compared with the radius (a) in the periodic solution.
Even in the case in which the time variation of the stress is a unit impulse, above results are found to hold.

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